This invention is directed to radiation curable oligomer compositions that are useful as coatings for various substrates.
There are many applications that require radiation curable coating compositions that are optically clear and resist penetration or absorption by water or chemicals. For example, barrier coatings and coatings for optical glass fibers should have these properties. Furthermore, barrier coatings and coatings for optical fibers should retain these properties over a broad temperature range.
Fluorine-containing polymers are very resistant to penetration by water and chemicals and therefore are well suited for use as barrier coatings. A patent application disclosing fluoropolymer claddings for optical fibers, designated AD-DO14 140 to Klinger et al., was published by the Office of the Chief of Naval Research on May 12, 1989. The cis-trans fluoropolyol polyacrylate coating is referred to therein as an infinite network fluoropolymer. As a result, the fluoropolymers disclosed in the Klinger et al. application have a very high molecular weight. These very high molecular weight fluoropolyol polyacrylate polymers, when used in coating compositions, are not easily applied to substrates.
U.S. Pat. No. 4,968,116discloses optical fiber coating compositions that comprise a fluorinated mono acrylate, a polyfunctional cross-linking acrylate and a photoinitiator.
The present invention is directed to radiation curable oligomer compositions that are curable by a free radical or a cationic mechanism.
The compositions of the present invention comprise a fluorinated urethane oligomer; at least one diluent monomer; and a photoinitiator. The fluorinated urethane oligomer is the reaction product of a fluorinated polyol, a polyisocyanate and an isocyanate reactive monomer containing ethylenic unsaturation. The isocyanate reactive monomer is preferably a (meth)acrylate, vinyl ether, maleate or fumarate. The diluent monomer is preferably a fluorinated monomer. The fluorinated urethane oligomer has a molecular weight in the range of about 700 to about 10,000, preferably about 1000 to about 5000.
The present invention also relates to methods of applying the above compositions to substrates and to substrates coated with the above compositions.